This invention relates to an induction control system for a multi-valve engine and more particularly to an induction system for engines that improves the performance throughout the engine speed and load ranges.
As is well known, turbulence in the combustion chamber of an internal combustion engine is a factor which can improve engine performance under some running conditions. However, like many other factors in engine design, the type and degree of turbulence desirable varies with engine running conditions.
There have been proposed, therefore, arrangements where the induction system is tuned and utilizes a control valve so that the degree of turbulence in the combustion chamber under different running conditions can be changed. For the most part, these systems provide either a first condition where there is turbulence and a second condition where the flow into the combustion chamber is relatively smooth and little or no turbulence is generated.
Some systems have been proposed in which one type of turbulence is generated under some running conditions and another type of turbulence may be generated under other running conditions. For example, induction systems have been proposed which generate swirl under some running conditions and tumble under other running conditions. As is well known, swirl is a motion in the combustion chamber wherein the intake charge tends to rotate about the cylinder bore axis. Tumble is a swirling motion that also occurs in the combustion chamber but the axis around which the swirl is created extends transversely to the cylinder bore axis.
This latter type of motion (tumble) is particularly advantageous because the degree of turbulence increases as the piston approaches top, dead-center conditions. That is, the tumbling charge in the combustion chamber has its velocity increased as the volume of the combustion chamber decreases.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine wherein the induction system can be operated so as to achieve different types of tumble in the combustion chamber under different running conditions.
It is a further object of this invention to provide an induction system for an engine wherein tumble in one direction may be generated under one running condition and tumble in an opposite direction may be generated under another running condition.
It has been found that the generation of different types or degrees of motion in the combustion chamber can be accomplished if each combustion chamber is provided with two or more intake valves and/or ports. It is, however, considerably easier to vary swirl through the use of multiple intake ports than it is tumble. One reason for this is that the tumble motion is dependent to a large extent on the location of the intake port relative to a plane containing the cylinder bore axis. The closer the port is to the cylinder bore axis the more easily tumble in one direction can be generated. If the intake port is, however, disposed so that it is further from the plane, than tumble in an opposite direction may be generated. Therefore, when valves having different placements relative to such a plane are employed for the same combustion chamber, the motion generated from one intake port may cancel out or reduce the effectiveness of the tumble from the other intake port.
It is, therefore, a still further object of this invention to provide an improved multiple port induction system for an engine wherein the desired degrees of turbulence can be generated without interfering action between the intake ports.